For many applications, such as telecommunications services, a reliable source of back-up power is critical. A back-up power system may employ an engine-driven alternator to generate electrical power. A combustion engine is used to drive an alternator which produces an AC voltage; the AC voltage may then be rectified to produce a DC voltage. An engine-driven alternator may come online whenever a commercial source of power is disrupted or, alternatively, the engine-driven alternator may be used to charge a battery plant, the battery plant providing a source of electrical power during interruptions in commercial power service.
Many back-up power systems must be placed in harsh environments, such as outdoor locations. In warm and/or arid climates, outdoor locations present the problem of adequate dissipation of heat generated by engine-driven alternators. To ensure system reliability, engine-driven alternators must not be allowed to overheat; thus, enclosures for containing such systems must provide sufficient airflow not only to cool the engine, but also to meet the fuel-mixture demands of the engine and carry exhaust gases out of the enclosure.
Back-up power systems employing engine-driven alternators must sometimes be placed in locations where persons other than trained service personnel may come into contact with them. Thus, such systems must not subject unsuspecting persons to any undue hazards. A conventional enclosure for an engine-driven alternator is constructed as a single-walled metal box; the box includes inlets for drawing ambient air into the enclosure and outlets for expelling exhaust gases. It has been observed, however, that single-walled enclosures may exhibit very-high surface temperatures due to stagnant air trapped within the enclosure; the stagnant air results in internal heat build-up that is transferred to the outer enclosure walls. Thus, although such conventional enclosures may be suitable for some applications, the enclosures do not adequately protect against excessive surface temperatures that may cause injury to unsuspecting persons.
In addition, back-up power systems employing engine-driven alternators are not always placed in remote locations, but may be placed near residences or work areas. Thus, such systems should not be obtrusive or a source of annoyance; for example, such systems should not create excessive noise. Unfortunately, engine-driven alternators inherently generate acoustic noise. To suppress the inherent noise, an enclosure must provide for noise isolation. It has been observed, however, that conventional single-walled enclosures do not adequately attenuate the inherent noise generated by engine-driven alternators.
Accordingly, what is needed in the art is a backup power system, employing an engine-driven alternator, that provides improved cooling airflow and which reduces the temperature of external enclosure surfaces and acoustic noise levels.